Despite the strong empirical evidence supporting the efficacy of CNS stimulants in the short-term treatment of Attention Deficit Hyperactivity Disorder (ADHD), controversies concerning its use continue. Prominent among these is whether cognitive-motivational factors that include children's control beliefs (i.e., attributions they make for the causes of their behavior and performance) both influence response to medication and are affected by medication. In particular, influential researchers have argued for some time that medication induces dysfunctional control beliefs in children with ADHD (i.e., they attribute their behavior and abilities to the medication), but there has been little systematic research on the topic. Many studies from the developmental literature on children's achievement have shown that attributions are important mediators of children's performance. If medicated ADHD boys tend to attribute their successes to medication and to blame themselves for their failures in life, then despite the salutary short-term effects of medication, they would be unlikely to demonstrate effortful, persistent behavior when faced with difficult social and academic situations. The purpose of the proposed series of studies is to examine the relationship between pharmacotherapy with methylphenidate and ADHD children's control beliefs, behavior, task persistence and self-evaluations. These studies are unique in three ways. First, with the exception of the preliminary studies discussed in this proposal, they constitute the first comprehensive examination of this important issue. Second, they involve the first application of a balanced placebo design (a design that completely crosses actual medication vs. placebo with expectation for medication vs. placebo) to pharmacotherapy for ADHD, thus affording the first investigation of ADHD children's expectancies on their response to medication. Third, they are the first studies to employ the current leading model of cognitive motivation from the developmental literature to pharmacotherapy of ADHD. Using this unique approach, 120 ADHD boys ranging in age from 8 to 13.6 will serve as subjects in three studies conducted over a four-year period. Study 1 will employ two laboratory tasks to study individual differences in the pharmacological vs expectancy effects of medication on ADHD children's task persistence under success vs. failure conditions in both academic and social domains of functioning. Study 2 will examine the pharmacological versus expectancy effects of medication on social and academic behavior, performance self-evaluations, and control beliefs of ADHD boys in the context of a summer treatment program. Study 3 will examine the same issues considered in Study 2 within the same children's regular school settings, thereby affording information regarding generalizability of the findings from the laboratory and treatment program studies. Given the importance of individual differences in this area of research, the design and analyses of all three studies will consider the effects of age, codiagnosis, and attributional style.